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NNTP Inter-Server Communication Process: News Article Propagation
(Page 2 of 4)
Basic NNTP Propagation Methods
Now let's look at how messages are
actually propagated between servers using NNTP. There are two techniques
by which this can be done:
- “Pushing” News: In the push
model, as soon as a server receives a new message, it immediately
tells its upstream and downstream neighbors about the message and asks
them if they want a copy of it.
- “Pulling” News: In the pull
model, servers do not offer new articles to their neighbors. The
neighboring servers must ask for a list of new messages if they want
to see what has arrived since the last connection was established, and
then request that the new messages be sent to them.
There are advantages and disadvantages
to both of these techniques, but pushing is the model most commonly
used today.
 Key Concept: One important role that NNTP plays is its propagation of articles between Usenet servers, which is what makes the entire system possible. Two models are used for article propagation: the push model, in which a server that receives a new message offers it to connected servers immediately, and the pull model, where servers that receive new messages hold them until they are requested by other servers. The push model is usually preferred since it allows for quicker communication of messages around the system.
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